1. Technical Field
The present invention relates to a process for blocking fluid flow in a soil, and more particularly to a process for placing a polymer enhanced foam in a soil to eliminate the flow capacity of a soil to a migratory fluid.
2. Description of Related Art
The utility of foams, and particularly polymer enhanced foams, has been demonstrated in numerous hydrocarbon recovery applications. For example, U.S. Pat. No. 5,129,457 discloses the utility of a polymer enhanced foam as a displacement fluid for recovering oil retained in vertical fractures of a subterranean oil-bearing formation. The same patent also discloses the utility of the polymer enhanced foam as a mobility control fluid in fractured formations ahead of a gas drive fluid. U.S. Pat. No. 4,856,588 likewise recognizes the effectiveness of specific foam compositions as a mobility control fluid ahead of a drive fluid in oil recovery applications. U.S. Pat. No. 3,393,738 discloses the utility of a polymer enhanced foam generated in situ for controlling leakage of stored gas in a subterranean formation containing mobile water. The foam can also improve the displacement of the mobile water from the formation, thereby increasing the gas storage capacity of the formation.
The conventional oil field foams taught by the above-disclosed prior art references reduce the permeability of relatively deep subterranean formations to certain fluids, but are not deemed useful in soil sealing applications near the surface because the foams retain a degree of mobility in contact with flowing liquids, such as liquid drive fluids or formation water, which is undesirable for soil sealing applications. Concerns regarding the mobility of conventional oil field foams in soil, which is generally less consolidated and more porous than the geological material of hydrocarbon-bearing formations, suggest the ineffectiveness of oil field foams in soil sealing applications.
For example, foams utilized as water sealants for shallow subterranean structures and surrounding soils are commonly held to require more resistance to water flow and greater durability in the near-surface environment than provided by conventional oil field foams. As such, a need exists for compositions that can effectively block the flow of migratory fluids through soils in a wide range of near-surface applications. In particular, soil sealing composition are needed that are relatively immobile in the soil when subjected to the natural drift pressure of migratory liquids flowing through the soil.
U.S. Pat. No. 3,894,131 discloses a conventional high-strength durable crosslinked polymer foam for near-surface water sealing applications. Such crosslinked polymer foams, however, present the user with another set of problems not encountered when using conventional oil field foams. The crosslinking reaction of the water sealing foam adds a higher degree of operational complexity to proper placement of the foam. In addition, referral of the foam, if subsequent removal of the foam is desired from the treatment region, can be very difficult. Finally, and importantly, the precrosslinked composition of the foam contains organic solvents posing a high degree of risk when introduced into the environment. The use of such materials in or near water lines and other water containments is often precluded in today's stricter environmental regulatory climate.
Accordingly, it is an object of the present invention to provide a soil treatment process for blocking flow of a migratory fluid in a soil. It is another object of the present invention to provide such a soil treatment process that is economical and operationally uncomplex. It is also an object of the present invention to provide such a soil treatment process that utilizes an effective fluid blocking composition. It is further an object of the present invention to provide such a soil treatment process that utilizes an environmentally compatible fluid blocking composition.